Electronic paper, as a display device driven by an electric field, becomes more and more popular due to such advantages as being easy to read, light, thin, flexible and power-saving. It is predicted that the market of the electronic paper will grow persistently and stably, more than 3.4 billion US dollars in the year of 2020.
The electronic paper is a thin film manufactured by coating tens of thousands of capsule-like particles (called as microcapsules) onto a plastic substrate. As a basic unit of the electronic paper, each microcapsule contains therein two kinds of nanoparticles in different colors, i.e., white titanium oxide particles and black carbon powder. Each white particle is positively charged, and each black particle is negatively charged. In the case that a negative electric field is applied onto an electrode plate at an upper surface of the electronic paper, the positively-charged white particles may be absorbed onto, and aggregated at, the electrode plate under the effect of the electric field, so as to enable the electrode plate to be in white. At the same time, the negatively-charged black particles are repelled to, and hidden at, a bottom electrode under the effect of the electric field. In the case that a positive electric field is applied onto the electrode plate at the upper surface of the electronic paper, the black particles move in an opposite direction, and so do the white particles. This is just a basic principle of the electronic paper.
Due to the bistability of the white and black particles, in the case that a static image is displayed, no power consumption may occur for the electronic paper. In other words, even in the case that no power is supplied, it is still able for the electronic paper to display a last image. However, in the case that content displayed on the electronic paper is to be rewritten after the electronic paper is powered off, it is necessary to power on the electronic paper again, so this operation is relatively complex. Undoubtedly, the market competitiveness of the electronic paper will be significantly increased by providing a writing function in a power off state.